PHY101 Solved MCQ'S For Exam

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1 PHY101 Solved MCQ'S For Exam Name: Date: 1. A right circular cylinder with a radius of 2.3 cm and a height of 1.4 cm has a total surface area of: A) m 2 B) m 2 C) m 3 D) m 2 E) m 2 2. A square with an edge of exactly 1 cm has an area of: A) 10 6 m 2 B) 10 4 m 2 C) 10 2 m 2 D) 10 4 m 2 E) 10 6 m 2 3. Suppose A = B n C m, where A has dimensions length time, B has dimensions length 2 time 1, and C has dimensions length time 2. Then the exponents n and m have the values: A) 2/3; 1/3 B) 2; 3 C) 4/5; 1/5 D) 1/5; 3/5 E) 1/2; 1/2 4. Which of the following weighs about a pound? A) 0.05 kg B) 0.5 kg C) 5 kg D) 50 kg E) 500 kg 5. The SI standard of time is based on: A) the daily rotation of the earth B) the frequency of light emitted by R 86 C) the yearly revolution of the earth about the sun D) a precision pendulum clock E) none of these Page 1

2 6. The SI standard of length is based on: A) the distance from the north pole to the equator along a meridian passing through Paris B) wavelength of light emitted by Hg 198 C) wavelength of light emitted by Kr 86 D) a precision meter stick in Paris E) the speed of light 7. 1 m is equivalent to ft. A cube with an edge of 1.5 ft has a volume of: A) m 3 B) m 3 C) 10.5 m 3 D) m 3 E) 0.21 m 3 8. There is no SI base unit for area because: A) an area has no thickness; hence no physical standard can be built B) we live in a three (not a two) dimensional world C) it is impossible to express square feet in terms of meters D) area can be expressed in terms of square meters E) area is not an important physical quantity 9. Which of the following is closest to a yard in length? A) 0.01 m B) 0.1 m C) 1 m D) 100 m E) 1000 m 10. A marble has a radius of 2 mm. The order of magnitude of the number of these marbles that can be placed in a jar with a radius of 3 cm and a height of 10 cm is: A) 10 B) 10 2 C) 10 4 D) 10 6 E) 19 8 Page 2

3 = A) B) C) D) E) The number of significant figures in 15.0 is: A) 1 B) 2 C) 3 D) 4 E) = A) 29 B) 28.8 C) 28.9 D) E) The order of magnitude of the number is: A) 2 B) C) 10 2 D) 10 1 E) = A) B) C) D) E) Page 3

4 16. A cubic box with an edge of exactly 1 cm has a volume of: A) 10 9 m 3 B) 10 6 m 3 C) 10 3 m 3 D) 10 3 m 3 E) 10 6 m A right circular cylinder with a radius of 2.3 cm and a height of 1.4 m has a volume of: A) 0.20 m 3 B) 0.14 m 3 C) m 3 D) m 3 E) m A nanosecond is: A) 10 9 s B) 10 9 s C) s D) s E) s 19. The SI base unit for mass is: A) gram B) pound C) kilogram D) ounce E) kilopound mi is equivalent to 1609 m so 55 mph is: A) 15 m/s B) 25 m/s C) 66 m/s D) 88 m/s E) 1500 m/s Page 4

5 Answer Key 1. D 2. B 3. D 4. B 5. E 6. E 7. B 8. D 9. C 10. C 11. C 12. C 13. B 14. D 15. E 16. B 17. D 18. B 19. C 20. B Page 5

6 Name: Date: 1. A car moving with an initial velocity of 25 m/s north has a constant acceleration of 3 m/s 2 south. After 6 seconds its velocity will be: A) 7 m/s north B) 7 m/s south C) 43 m/s north D) 20 m/s north E) 20 m/s south 2. A car starts from rest and goes down a slope with a constant acceleration of magnitude 5 m/s 2. After 5 s its speed, in meters per second, is: A) 1 B) 12.5 C) 25 D) 50 E) The velocity of an object is given as a function of time by v = (4t 3 t )î, where v is in m/s and t is in seconds. Its average velocity over the interval from t = 0 to t = 2 s: A) is 0 B) is ( 2 m/s) î C) is (2 m/s) î D) is ( 4 m/s) î E) cannot be calculated unless the initial position is given 4. The diagram shows a velocity-time graph for a car moving in a straight line. At point P the car must be: A) moving with zero acceleration B) climbing the hill C) accelerating D) stationary E) moving at about 45 º with respect to the x axis Page 1

7 5. A car travels 40 kilometers at an average speed of 80 km/h and then travels 40 kilometers at an average speed of 40 km/h. The average speed of the car for this 80-km trip is: A) 40 km/h B) 45 km/h C) 48 km/h D) 53 km/h E) 80 km/h 6. The diagram represents the straight line motion of a car. Which of the following statements is true? A) The car accelerates, stops, and reverses B) The car accelerates at 6 m/s 2 for the first 2 s C) The car is moving for a total time of 12 s D) The car decelerates at 12 m/s 2 for the last 4 s E) The car returns to its starting point when t = 9 s 7. A racing car traveling with constant acceleration increases its speed from 10 m/s to 50 m/s over a distance of 60 m. How long does this take? A) 2.0 s B) 4.0 s C) 5.0 s D) 8.0 s E) The time cannot be calculated since the speed is not constant 8. The coordinate-time graph of an object is a straight line with a positive slope. The object has: A) constant displacement B) steadily increasing acceleration C) steadily decreasing acceleration D) constant velocity E) steadily increasing velocity Page 2

8 9. A particle moves along the x axis from x1 to x2. Of the following values of the initial and final coordinates, which results in the displacement with the largest magnitude? A) x1 = 4 m, x2 = 6 m B) x1 = 4 m, x2 = 8 m C) x1 = 4 m, x2 = 2 m D) x1 = 4 m, x2 = 2 m E) x1 = 4 m, x2 = 4 m 10. A particle moves along the x axis from x1 to x2. Of the following values of the initial and final coordinates, which results in a displacement that is in the negative x direction? A) x1 = 4 m, x2 = 6 m B) x1 = 4 m, x2 = 8 m C) x1 = 4 m, x2 = 2 m D) x1 = 4 m, x2 = 2 m E) x1 = 4 m, x2 = 4 m 11. A car accelerates from rest on a straight road. A short time later, the car decelerates to a stop and then returns to its original position in a similar manner, by first speeding up and then slowing to a stop. Which of the following five coordinate versus time graphs best describes the motion? A) A B) B C) C D) D E) E Page 3

9 12. Throughout a time interval, while the speed of a particle increases as it moves along the x axis, its velocity and acceleration: A) might be in the positive and negative x directions, respectively B) might be in the negative and positive x directions, respectively C) might both be in the negative x direction D) might be in the negative x direction and zero, respectively E) might be in the positive x direction and zero, respectively 13. At time t = 0 a car has a velocity of (16 m/s) î. It slows down with an acceleration given by ( 0.50 m/s 3 )t î. By the time it stops it has traveled: A) 15 m B) 31 m C) 62 m D) 85 m E) 100 m 14. A car starts from Hither, goes 50 km in a straight line to Yon, immediately turns around, and returns to Hither. The time for this round trip is 2 hours. The average speed of the car for this round trip is: A) 0 B) 50 km/h C) 100 km/h D) 200 km/h E) cannot be calculated without knowing the acceleration Page 4

10 15. Which of the following five coordinate versus time graphs represents the motion of an object moving with a constant nonzero speed? A) A B) B C) C D) D E) E 16. The graph represents the straight line motion of a car. How far does the car travel between t = 2 s and t = 5 s? A) 4 m B) 12 m C) 24 m D) 36 m E) 60 m Page 5

11 17. Over a short interval, starting at time t = 0, the coordinate of an automobile in meters is given by x(t) = 27t 4.0t 3, where t is in seconds. The magnitudes of the initial (at t = 0) velocity and acceleration of the auto respectively are: A) 0; (12 m/s 2 ) î B) 0; (24 m/s 2 ) î C) (27 m/s) î; 0 D) (27 m/s) î; (12 m/s 2 ) î E) (27 m/s) î; (24 m/s 2 ) î 18. A particle moves along the x axis according to the equation x = 6t 2, where x is in meters and t is in seconds. Therefore: A) the acceleration of the particle is (6 m/s 2 ) î B) t cannot be negative C) the particle follows a parabolic path D) each second the speed of the particle changes by 9.8 m/s E) none of the above 19. Two automobiles are 150 kilometers apart and traveling toward each other on a straight road. One automobile is moving at 60 km/h and the other is moving at 40 km/h mph. In how many hours will they meet? A) 2.5 B) 2.0 C) 1.75 D) 1.5 E) Over a short interval near time t = 0 the coordinate of an automobile in meters is given by x(t) = 27t 4.0t 3, where t is in seconds. At the end of 1.0 s the acceleration of the auto is: A) (27 m/s 2 ) î B) (4.0 m/s 2 ) î C) ( 4.0 m/s 2 ) î D) ( 12 m/s 2 ) î E) ( 24 m/s 2 ) î Page 6

12 Answer Key 1. A 2. C 3. A 4. C 5. D 6. B 7. B 8. D 9. E 10. B 11. E 12. C 13. D 14. B 15. B 16. D 17. C 18. E 19. D 20. E Page 7

13 Name: Date: 1. A ball is in free fall. Upward is taken to be the positive direction. The displacement of the ball during a short time interval is: A) positive during both ascent and descent B) negative during both ascent and descent C) negative during ascent and positive during descent D) positive during ascent and negative during descent E) none of the above 2. An object is thrown straight down with an initial speed of 4 m/s from a window which is 8 m above the ground. The time it takes the object to reach the ground is: A) 0.80 s B) 0.93 s C) 1.3 s D) 1.7 s E) 2.0 s 3. A car travels east at constant velocity. The net force on the car is: A) east B) west C) up D) down E) zero 4. A freely falling body has a constant acceleration with a magnitude of 9.8 m/s 2. This means that: A) the body falls 9.8 m during each second B) the body falls 9.8 m during the first second only C) the speed of the body increases by 9.8 m/s during each second D) the magnitude of the acceleration of the body increases by 9.8 m/s 2 during each second E) the magnitude of the acceleration of the body decreases by 9.8 m/s 2 during each second Page 1

14 5. When a certain force is applied to the standard kilogram its acceleration is 5.0 m/s 2. When the same force is applied to another object its acceleration is one-fifth as much. The mass of the object is: A) 0.2 kg B) 0.5 kg C) 1.0 kg D) 5.0 kg E) 10 kg 6. An object dropped from the window of a tall building hits the ground in 12.0 s. If its acceleration has a magnitude of 9.80 m/s 2, the height of the window above the ground is: A) 29.4 m B) 58.8 m C) 118 m D) 353 m E) 706 m 7. One object is thrown vertically upward with an initial velocity of 100 m/s and another object with an initial velocity of 10 m/s. The maximum height reached by the first object will be that of the other. A) 10 times B) 100 times C) 1000 times D) 10,000 times E) none of these 8. An object is thrown straight up from ground level with a speed of 50 m/s. If the magnitude of the local gravitational strength is g = 10 N/kg its distance above ground level 6.0 s later is: A) 0.00 m B) 270 m C) 330 m D) 480 m E) none of these Page 2

15 9. Three books (X, Y, and Z) rest on a table. The gravitational force on each book is indicated. The net force on book Y is: A) 4 N down B) 5 N up C) 9 N down D) zero E) none of these 10. A feather and a lead ball are dropped from rest in vacuum on the Moon. The acceleration of the feather is: A) more than that of the lead ball B) the same as that of the lead ball C) less than that of the lead ball D) 9.8 m/s 2 E) zero since it floats in a vacuum 11. Acceleration is always in the direction: A) of the displacement B) of the initial velocity C) of the final velocity D) of the net force E) opposite to the frictional force 12. An example of an inertial reference frame is: A) any reference frame that is not accelerating B) a reference frame attached to a particle on which there are no forces C) any reference frame that is at rest D) a reference frame attached to the center of the universe E) a reference frame attached to Earth 13. An object rests on a horizontal frictionless surface. A horizontal force of magnitude F is applied. This force produces an acceleration: A) only if F is larger than the weight of the object B) only while the object suddenly changes from rest to motion C) always D) only if the inertia of the object decreases E) only if F is increasing Page 3

16 14. An object is thrown straight up from ground level with a speed of 50 m/s. If g = 10 m/s 2 its distance above ground level 1.0 s later is: A) 40 m B) 45 m C) 50 m D) 55 m E) 60 m 15. A lead block is suspended from your hand by a string. The reaction to the force of gravity on the block is the force exerted by: A) the string on the block B) the block on the string C) the string on the hand D) the hand on the string E) the block on Earth 16. A heavy ball is suspended as shown. A quick jerk on the lower string will break that string but a slow pull on the lower string will break the upper string. The first result occurs because: A) the force is too small to move the ball B) action and reaction is operating C) the ball has inertia D) air friction holds the ball back E) the ball has too much energy 17. The unit of force called the newton is: A) 9.8 kg m/s 2 B) 1 kg m/s 2 C) defined by means of Newton's third law D) 1 kg of mass E) 1 kg of force Page 4

17 18. A newton is the force: A) of gravity on a 1 kg body B) of gravity on a 1 g body C) that gives a 1 g body an acceleration of 1 cm/s 2 D) that gives a 1 kg body an acceleration of 1 m/s 2 E) that gives a 1 kg body an acceleration of 9.8 m/s A stone is released from rest from the edge of a building roof 190 m above the ground. Neglecting air resistance, the speed of the stone, just before striking the ground, is: A) 43 m/s B) 61 m/s C) 120 m/s D) 190 m/s E) 1400 m/s 20. Three blocks (A,B,C), each having mass M, are connected by strings as shown. Block C is pulled to the right by a force F that causes the entire system to accelerate. Neglecting friction, the net force on block B is: A) zero B) F/ 3 C) F/ 2 D) 2F/ 3 E) F Page 5

18 Answer Key 1. D 2. B 3. E 4. C 5. D 6. E 7. B 8. E 9. D 10. B 11. D 12. B 13. C 14. B 15. E 16. C 17. B 18. D 19. B 20. B Page 6

19 Name: Date: 1. Vectors A and B lie in the xy plane. We can deduce that A = B if: A) Ax 2 + Ay 2 = Bx 2 + By 2 B) Ax + Ay = Bx + By C) Ax = Bx and Ay = By D) Ay/Ax = By/Bx E) Ax = Ay and Bx = By 2. In the diagram, A has magnitude 12 m and B has magnitude 8 m. The x component of A+ B is about: A) 5.5 m B) 7.6 m C) 12 m D) 14 m E) 15 m 3. The vector V 3 in the diagram is equal to: A) V1 V 2 B) V1+ V 2 C) 2 1 V V D) V cos 1 θ E) V (cos θ) 1 Page 1

20 4. A certain vector in the xy plane has an x component of 4 m and a y component of 10 m. It is then rotated in the xy plane so its x component is doubled. Its new y component is about: A) 20 m B) 7.2 m C) 5.0 m D) 4.5 m E) 2.2 m 5. If A= (2m)i ˆ (3m) ˆj and B = (1m) ˆi (2 m) ˆj, then A 2B = A) (1m) ˆj B) ( 1m)j ˆ C) (4m)i ˆ (7m) ˆj D) (4m)i ˆ+ (1m) ˆj E) ( 4m)i ˆ+ (7m)j ˆ 6. In the expressions r = x ˆi+ y ˆ j for the position vector of a particle and v = v ˆi+ v ˆj its velocity: A) the unit vector î might have a unit of meters B) î and ĵ are both variables C) î represents a different vector in the two expressions D) î and ĵ are parallel to each other E) none of the above x y for 7. The angle between A = (25m)i ˆ+ (45m)j ˆ A) 29º B) 61º C) 151º D) 209º E) 241º and the positive x axis is: Page 2

21 8. Let A = (2m)i ˆ+ (6m) ˆj (3m)kˆ D = A B is: A) (6m) ˆi + (8m) ˆj (2m) kˆ B) ( 2m)i ˆ+ (4m) ˆj (4m)kˆ C) (2m)i ˆ (4m) ˆj + (4m)kˆ D) (8m)i ˆ+ (12m) ˆj (3m)kˆ E) none of these and B = (4m)i ˆ+ (2mˆj + (1m)kˆ. The vector difference 9. A vector has a component of 10 m in the + x direction, a component of 10 m in the + y direction, and a component of 5 m in the + z direction. The magnitude of this vector is: A) zero B) 15 m C) 20 m D) 25 m E) 225 m 10. The angle between A = ( 25m)i ˆ+ (45m)j ˆ A) 29º B) 61º C) 119º D) 151º E) 209º and the positive x axis is: 11. The vectors a, b, and c are related by c = b a. Which diagram below illustrates this relationship? A) A B) B C) C D) D E) None of these Page 3

22 If A + B = A + B, then: A) A and B must be parallel and in the same direction B) A and B must be parallel and in opposite directions C) either A or B must be zero D) the angle between A and B must be 60º E) none of the above is true 13. A vector in the xy plane has a magnitude of 25 m and an x component of 12 m. The angle it makes with the positive x axis is: A) 26º B) 29º C) 61º D) 64º E) 241º 14. Let V = (2. 00m)i ˆ+ (6. 00m) ˆj (3. 00m)kˆ. The magnitude of V is: A) 5.00 m B) 5.57 m C) 7.00 m D) 7.42 m E) 8.54 m 15. If A + B = A + Band neither A nor B vanish, then: A) A and B are parallel and in the same direction B) A and B are parallel and in opposite directions C) the angle between A and B is 45º D) the angle between A and B is 60º E) A is perpendicular to B 16. Let A = (2m)i ˆ+ (6m) ˆj (3m)kˆ S= A + B is: A) (6m)i ˆ+ (8m) ˆj (2m)kˆ B) ( 2m)i ˆ+ (4m)j ˆ (4m)kˆ C) (2m)i ˆ (4m) ˆj + (4m)kˆ D) (8 m) ˆi + (12 m) ˆj (3m) kˆ E) none of these and B = (4m)i ˆ+ (2m) ˆj + (1m)kˆ. The vector sum Page 4

23 17. A vector of magnitude 3 CANNOT be added to a vector of magnitude 4 so that the magnitude of the resultant is: A) zero B) 1 C) 3 D) 5 E) Four vectors ( A, B, C, D ) all have the same magnitude. The angle θ between adjacent vectors is 45º as shown. The correct vector equation is: A) A B C + D = 0 B) B + D 2C = 0 C) A + B = B + D D) A + B + C + D = 0 E) ( A + C) / 2 = B 19. We say that the displacement of a particle is a vector quantity. Our best justification for this assertion is: A) displacement can be specified by a magnitude and a direction B) operating with displacements according to the rules for manipulating vectors leads to results in agreement with experiments C) a displacement is obviously not a scalar D) displacement can be specified by three numbers E) displacement is associated with motion 20. If A = (6 m) ˆi (8m) ˆj A) 10 m B) 20 m C) 30 m D) 40 m E) 50 m then 4A has magnitude: Page 5

24 Answer Key 1. C 2. C 3. C 4. B 5. A 6. E 7. B 8. B 9. B 10. C 11. D 12. E 13. C 14. C 15. A 16. A 17. A 18. B 19. B 20. D Page 6

25 Name: Date: 1. A boy on the edge of a vertical cliff 20 m high throws a stone horizontally outward with a speed of 20 m/s. It strikes the ground at what horizontal distance from the foot of the cliff? Use g = 10 m/s 2. A) 10 m B) 40 m C) 50 m D) 50 5 m E) none of these 2. A cannon fires a projectile as shown. The dashed line shows the trajectory in the absence of gravity; points MNOP correspond to the positions of the particle at one second intervals. Using g = 10 N/kg, the lengths X,Y,Z are: A) 5 m, 10 m, 15 m B) 5 m, 20 m, 45 m C) 10 m, 40 m, 90 m D) 10 m, 20 m, 30 m E) 0.2 m, 0.8 m, 1.8 m Page 1

26 3. A stone is thrown horizontally and follows the path XYZ shown. The direction of the acceleration of the stone at point Y is: A) B) C) D) E) 4. A particle moves at constant speed in a circular path. The instantaneous velocity and instantaneous acceleration vectors are: A) both tangent to the circular path B) both perpendicular to the circular path C) perpendicular to each other D) opposite to each other E) none of the above 5. A stone thrown from the top of a tall building follows a path that is: A) circular B) made of two straight line segments C) hyperbolic D) parabolic E) a straight line 6. An object is shot from the back of a railroad flatcar moving at 40 km/h on a straight horizontal road. The launcher is aimed upward, perpendicular to the bed of the flatcar. The object falls: A) in front of the flatcar B) behind the flatcar C) on the flatcar D) either behind or in front of the flatcar, depending on the initial speed of the object E) to the side of the flatcar Page 2

27 7. A stone is thrown outward from the top of a 59.4-m high cliff with an upward velocity component of 19.5 m/s. How long is the stone in the air? A) 4 s B) 5 s C) 6 s D) 7 s E) 8 s 8. A car rounds a 20-m radius curve at 10 m/s. The magnitude of its acceleration in is: A) 0 B) 0.20 m/s 2 C) 5.0 m/s 2 D) 40 m/s 2 E) 400 m/s 2 9. A bullet shot horizontally from a gun: A) strikes the ground much later than one dropped vertically from the same point at the same instant B) never strikes the ground C) strikes the ground at approximately the same time as one dropped vertically from the same point at the same instant D) travels in a straight line E) strikes the ground much sooner than one dropped from the same point at the same instant 10. Acceleration is defined as: A) rate of change of position with time B) speed divided by time C) rate of change of velocity with time D) a speeding up or slowing down E) change of velocity 11. An object is moving on a circular path of radius π meters at a constant speed of 4.0 m/s. The time required for one revolution is: A) 2/π 2 s B) π 2 /2 s C) π/2 s D) π 2 /4 s E) 2/π s Page 3

28 12. An object moving in a circle at constant speed: A) must have only one force acting on it B) is not accelerating C) is held to its path by centrifugal force D) has an acceleration of constant magnitude E) has an acceleration that is tangent to the circle 13. An airplane is flying north at 500 km/h. It makes a gradual 180º turn at constant speed, changing its direction of travel from north through east to south. The process takes 40 s. The average acceleration of the plane for this turn is: A) 12.5 m/s 2, north B) 12.5 m/s 2, east C) 12.5 m/s 2, south D) 25 m/s 2, north E) 25 m/s 2, south 14. The airplane shown is in level flight at an altitude of 0.50 km and a speed of 150 km/h. At what distance d should it release a heavy package to hit the target X? Take the magnitude of the local gravitational strength to be 10 N/kg 2. A) 150 m B) 295 m C) 420 m D) 2550 m E) 15,000 m Page 4

29 15. If a certain car, going with speed v1, rounds a level curve with a radius R1, it is just on the verge of skidding. If its speed is now doubled, the radius of the tightest curve on the same road, with the same force on the car, that it can round is: A) 2R1 B) 4R1 C) R1/2 D) R1/4 E) R1 16. A giant wheel, having a diameter of 40 m, is fitted with a cage and platform on which a man of mass m stands. The wheel is rotated in a vertical plane at such a speed that the force exerted by the man on the platform is equal to his weight when the cage is at X, as shown. The net force on the man at point X is: A) zero B) mg, down C) mg, up D) 2mg, down E) 2mg, up 17. A large cannon is fired from ground level over level ground at an angle of 30º above the horizontal. The muzzle speed is 980 m/s. Neglecting air resistance, the projectile will travel what horizontal distance before striking the ground? A) 4.3 km B) 8.5 km C) 43 km D) 85 km E) 170 km Page 5

30 18. An airplane makes a gradual 90º turn while flying at a constant speed of 200 m/s. The process takes 20.0 seconds to complete. For this turn the magnitude of the average acceleration of the plane is: A) zero B) 40 m/s 2 C) 20 m/s 2 D) 14 m/s 2 E) 10 m/s Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If one of the bodies is given an additional horizontal acceleration during its descent, it: A) strikes the plane at the same time as the other body B) strikes the plane earlier than the other body C) has the vertical component of its velocity altered D) has the vertical component of its acceleration altered E) follows a straight line path along the resultant acceleration vector 20. A stone is tied to the end of a string and is swung with constant speed around a horizontal circle with a radius of 1.5 m. If it makes two complete revolutions each second, the magnitude of its acceleration is: A) 0.24 m/s 2 B) 2.4 m/s 2 C) 24 m/s 2 D) 240 m/s 2 E) 2400 m/s 2 Page 6

31 Answer Key 1. B 2. B 3. A 4. C 5. D 6. C 7. C 8. C 9. C 10. C 11. B 12. D 13. E 14. C 15. B 16. D 17. D 18. D 19. A 20. D Page 7

32 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page 1 Name: Date: 1. A crate resting on a rough horizontal floor is to be moved horizontally. The coefficient of static friction is To start the crate moving with the weakest possible applied force, in what direction should the force be applied? A) Horizontal B) 24º below the horizontal C) 22º above the horizontal D) 24º above the horizontal E) 66º below the horizontal 2. A 70-N block and a 35-N block are connected by a string as shown. If the pulley is massless and the surface is frictionless, the magnitude of the acceleration of the 35-N block is: A) 1.6 m/s 2 B) 3.3 m/s 2 C) 4.9 m/s 2 D) 6.7 m/s 2 E) 9.8 m/s 2

33 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page 2 3. Two blocks are connected by a string and pulley as shown. Assuming that the string and pulley are massless, the magnitude of the acceleration of each block is: A) m/s 2 B) m/s 2 C) m/s 2 D) 0.54 m/s 2 E) 0.98 m/s 2 4. Block A, with a mass of 10 kg, rests on a 35º incline. The coefficient of static friction is An attached string is parallel to the incline and passes over a massless, frictionless pulley at the top. The largest mass mb of block B, attached to the dangling end, for which A remains at rest is: A) 2.5 kg B) 3.5 kg C) 5.9 kg D) 9.0 kg E) 10.5 kg

34 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page 3 5. When a 40-N force, parallel to the incline and directed up the incline, is applied to a crate on a frictionless incline that is 30º above the horizontal, the acceleration of the crate is 2.0 m/s 2, up the incline. The mass of the crate is: A) 3.8 kg B) 4.1 kg C) 5.8 kg D) 6.2 kg E) 10 kg 6. A 90-kg man stands in an elevator that has a downward acceleration of 1.4 m/s 2. The force exerted by him on the floor is about: A) zero B) 90 N C) 760 N D) 880 N E) 1010 N 7. Block A, with a mass of 10 kg, rests on a 30º incline. The coefficient of kinetic friction is The attached string is parallel to the incline and passes over a massless, frictionless pulley at the top. Block B, with a mass of 8.0 kg, is attached to the dangling end of the string. The acceleration of B is: A) 0.69 m/s 2, up the plane B) 0.69 m/s 2, down the plane C) 2.6 m/s 2, up the plane D) 2.6 m/s 2, down the plane E) 0

35 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page 4 8. A force F (larger than the largest possible force of static friction) is applied to the left to an object moving to the right on a horizontal surface. Then: A) the object must be moving at constant speed B) F and the friction force act in opposite directions C) the object must be slowing down D) the object must be speeding up E) the object must come to rest and remain at rest 9. A boy pulls a wooden box along a rough horizontal floor at constant speed by means of a force P as shown. In the diagram f is the magnitude of the force of friction, N is the magnitude of the normal force, and Fg is the magnitude of the force of gravity. Which of the following must be true? A) P = f and N = Fg B) P = f and N > Fg C) P > f and N < Fg D) P > f and N = Fg E) none of these 10. The system shown remains at rest. Each block weighs 20 N. The force of friction on the upper block is: A) 4 N B) 8 N C) 12 N D) 16 N E) 20 N

36 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page A 25-kg crate is pushed across a frictionless horizontal floor with a force of 20 N, directed 20º below the horizontal. The acceleration of the crate is: A) 0.27 m/s 2 B) 0.75 m/s 2 C) 0.80 m/s 2 D) 170 m/s 2 E) 470 m/s A car is traveling at 15 m/s on a horizontal road. The brakes are applied and the car skids to a stop in 4.0 s. The coefficient of kinetic friction between the tires and road is: A) 0.38 B) 0.69 C) 0.76 D) 0.92 E) A horizontal force of 5.0 N pushes a 0.50-kg book against a vertical wall. The book is initially at rest. If μ static = 0.6 and μ kin = 0.80 are the coefficients of friction, the magnitude of the frictional force is: A) 0 B) 4.9 N C) 3.0 N D) 5.0 N E) 4.0 N

37 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page Block A, with a mass of 10 kg, rests on a 35º incline. The coefficient of static friction is An attached string is parallel to the incline and passes over a massless, frictionless pulley at the top. The largest mass mb of block B, attached to the dangling end, for which A begins to slide down the incline is: A) 2.5 kg B) 3.5 kg C) 5.9 kg D) 9.0 kg E) 10.5 kg 15. A heavy wooden block is dragged by a force F along a rough steel plate, as shown in the diagrams for two cases. The magnitude of the applied force F is the same for both cases. The normal force in (ii), as compared with the normal force in (i) is: A) the same B) greater C) less D) less for some angles of the incline and greater for others E) less or greater, depending on the magnitude of the applied force F.

38 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page Two forces, one with a magnitude of 3 N and the other with a magnitude of 5 N, are applied to an object. For which orientations of the forces shown in the diagrams is the magnitude of the acceleration of the object the least? A) A B) B C) C D) D E) E 17. A car rounds a 75-m radius curve at a constant speed of 18 m/s. A ball is suspended by a string from the ceiling the car and moves with the car. The angle between the string and the vertical is: A) 0 B) 1.4º C) 24º D) 90º E) cannot be found without knowing the mass of the ball 18. A brick slides on a horizontal surface. Which of the following will increase the frictional force on it? A) Putting a second brick on top B) Decreasing the surface area of contact C) Increasing the surface area of contact D) Decreasing the mass of the brick E) None of the above

39 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page A crate is sliding down an incline that is 35º above the horizontal. If the coefficient of kinetic friction is 0.40, the acceleration of the crate is: A) 0 B) 2.4 m/s 2 C) 5.8 m/s 2 D) 8.8 m/s 2 E) 10.3 m/s A ball is thrown upward into the air with a speed that is greater than terminal speed. It lands at the place where it was thrown. During its flight the force of air resistance is the greatest: A) just after it is thrown B) halfway up C) at the top of its trajectory D) halfway down E) just before it lands.

40 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page 9 Answer Key 1. C 2. B 3. E 4. D 5. C 6. C 7. B 8. C 9. C 10. B 11. B 12. A 13. E 14. A 15. C 16. A 17. C 18. A 19. B 20. A

41 University Physics (Prof. David Flory) Chapt_07 Saturday, October 06, 2007 Page 1 Name: Date: 1. A stream of gas consists of n molecules. Each molecule has mass m and speed v. Each molecule is reflected without change in speed from a rigid surface as shown. The magnitude of the change in the total momentum of the stream is: A) 2mnv B) 2mnv sin 30º C) mnv sin 30º D) mnv cos 30º E) mnv 2. A golf ball of mass m is hit by a golf club so that the ball leaves the tee with speed v. The club is in contact with the ball for time T. The magnitude of the average force on the club on the ball during the time T is: A) mvt B) mv/t C) (1/2)mv 2 T D) mv 2 /(2T) E) mt 2 /(2v) 3. A 0.2-kg rubber ball is dropped from the window of a building. It strikes the sidewalk below at 30 m/s and rebounds up at 20 m/s. The impulse on the ball during the collision is: A) 10 N s upward B) 10 N s downward C) 2.0 N s upward D) 2.0 N s downward E) 9.8 N s upward

42 University Physics (Prof. David Flory) Chapt_07 Saturday, October 06, 2007 Page 2 4. The thrust of a rocket is: A) a gravitational force acting on the rocket B) the force of the exiting fuel gases on the rocket C) any force that is external to the rocket-fuel system D) a force that arises from the reduction in mass of the rocket-fuel system E) none of the above 5. A 64-kg woman stands on frictionless level ice, with a 0.10-kg stone at her feet. She kicks the stone with her foot so that she acquires a velocity of m/s in the forward direction. The velocity acquired by the stone is: A) 1.1 m/s forward B) 1.1 m/s backward C) m/s forward D) m/s backward E) none of these 6. A ball hits a wall and rebounds with the same speed, as diagramed below. The changes in the components of the momentum of the ball are: A) Δpx > 0, Δpy > 0 B) Δpx < 0, Δpy > 0 C) Δpx = 0, Δpy > 0 D) Δpx = 0, Δpy < 0 E) Δpx > 0, Δpy < 0

43 University Physics (Prof. David Flory) Chapt_07 Saturday, October 06, 2007 Page 3 7. A 500-kg sack of coal is dropped on a 2000-kg railroad flatcar which was initially moving at 3 m/s as shown. After the sack rests on the flatcar, the speed of the flatcar is: A) 0.6 m/s B) 1.2 m/s C) 1.8 m/s D) 2.4 m/s E) 3.6 m/s 8. Bullets from two revolvers are fired with the same velocity. The bullet from gun #1 is twice as heavy as the bullet from gun #2. Gun #1 weighs three times as much as gun #2. The ratio of the momentum imparted to gun #1 to that imparted to gun #2 is: A) 2:3 B) 3:2 C) 2:1 D) 3:1 E) 6:1 9. What impulse will give a 2.0-kg object a momentum change of + (50 kg m/ s) ˆi? A) + (25N s)i ˆ B) (25N s)i ˆ C) + (50 N s) ˆi D) (50 N s) ˆi E) + (100 N s) ˆi

44 University Physics (Prof. David Flory) Chapt_07 Saturday, October 06, 2007 Page A 3.00-g bullet traveling horizontally at 400 m/s hits a 3.00-kg wooden block, which is initially at rest on a smooth horizontal table. The bullet buries itself in the block without passing through. The speed of the block after the collision is: A) 1.33 m/s B) 0.40 m/s C) 12.0 m/s D) 40.0 m/s E) 160 m/s 11. A rifle of mass M is initially at rest but free to recoil. It fires a bullet of mass m and velocity v (relative to the ground). After firing, the velocity of the rifle (relative to the ground) is: A) mv B) Mv/m C) mv/m D) v E) mv/m 12. A 75-kg man is riding in a 30-kg cart at 2.0 m/s. He jumps off in such a way as to land on the ground with no horizontal velocity. The resulting change in speed of the cart is: A) zero B) 2.0 m/s C) 3.0 m/s D) 5.0 m/s E) 7.0 m/s 13. A man is marooned at rest on level frictionless ice. In desperation, he hurls his shoe to the right at 15 m/s. If the man weighs 720 N and the shoe weighs 4.0 N, the man moves to the left with a speed of: A) 0 B) m/s C) m/s D) 15 m/s E) m/s

45 University Physics (Prof. David Flory) Chapt_07 Saturday, October 06, 2007 Page A large wedge with a mass of 10 kg rests on a horizontal frictionless surface, as shown. A block with a mass of 5.0 kg starts from rest and slides down the inclined surface of the wedge, which is rough. At one instant the vertical component of the block's velocity is 3.0 m/s and the horizontal component is 6.0 m/s. At that instant the velocity of the wedge is: A) 3.0 m/s to the left B) 3.0 m/s to the right C) 6.0 m/s to the right D) 6.0 m/s to the left E) 17 m/s to the right 15. A 640-N acrobat falls 5.0 m from rest into a net. The net tosses him back up with the same speed he had just before he hit the net. The magnitude of the average upward force exerted on him by the net during this collision is: A) 32 N B) 64 N C) 320 N D) 640 N E) impossible to determine from the given data 16. When you step on the accelerator to increase the speed of your car, the force that accelerates the car is: A) the force of your foot on the accelerator B) the force of friction of the road on the tires C) the force of the engine on the drive shaft D) the normal force of the road on the tires E) none of the above

46 University Physics (Prof. David Flory) Chapt_07 Saturday, October 06, 2007 Page A 5-kg object can move along the x axis. It is subjected to a force F in the positive x direction; a graph of Fx as a function of time t is shown below. Over the time the force is applied the change in the velocity of the object is: A) 0.8 m/s B) 1.1 m/s C) 1.6 m/s D) 2.3 m/s E) 4.0 m/s 18. At one instant of time a rocket is traveling in outer space at 2500 m/s and is exhausting fuel at a rate of 100 kg/s. If the speed of the fuel as it leaves the rocket is 1500 m/s, relative to the rocket, the thrust is: A) 0 B) N C) N D) N E) N 19. The momentum of an object at a given instant is independent of its: A) inertia B) mass C) speed D) velocity E) acceleration

47 University Physics (Prof. David Flory) Chapt_07 Saturday, October 06, 2007 Page The physical quantity impulse has the same dimensions as that of: A) force B) power C) energy D) momentum E) work

48 University Physics (Prof. David Flory) Chapt_07 Saturday, October 06, 2007 Page 8 Answer Key 1. B 2. B 3. A 4. B 5. B 6. C 7. D 8. C 9. C 10. B 11. C 12. D 13. C 14. B 15. E 16. B 17. A 18. C 19. E 20. D

49 University Physics (Prof. David Flory) Chapt_08 Saturday, October 06, 2007 Page 1 Name: Date: 1. A machinist starts with three identical square plates but cuts one corner from one of them, two corners from the second, and three corners from the third. Rank the three plates according to the x coordinate of their centers of mass, from smallest to largest. A) 1, 2, 3 B) 1 and 2 tie, then 3 C) 1, then 2 and 3 tie D) 3, 2, 1 E) 1 and 3 tie, then 2 2. At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s. They move along nearby lines and pass each other without colliding. At the end of 2.0 s the height above Earth's surface of the center of mass of the two-ball system is: A) 2.9 m B) 4.0 m C) 5.0 m D) 7.1 m E) 10.4 m

50 University Physics (Prof. David Flory) Chapt_08 Saturday, October 06, 2007 Page 2 3. Two boys, with masses of 40 kg and 60 kg, respectively, stand on a horizontal frictionless surface holding the ends of a light 10-m long rod. The boys pull themselves together along the rod. When they meet the 60-kg boy will have moved what distance? A) 4 m B) 5 m C) 6 m D) 10 m E) need to know the forces they exert 4. A 640-N hunter gets a rope around a 3200-N polar bear. They are stationary, 20 m apart, on frictionless level ice. When the hunter pulls the polar bear to him, the polar bear will move: A) 1.0 m B) 3.3 m C) 10 m D) 12 m E) 17 m 5. At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s. They move along nearby lines and pass without colliding. At the end of 2.0 s the magnitude of the acceleration of the center of mass of the two-ball system is: A) 0.25g B) 0.50g C) 0.75g D) g E) g/ A light rope passes over a light frictionless pulley attached to the ceiling. An object with a large mass is tied to one end and an object with a smaller mass is tied to the other end. Starting from rest the heavier object moves downward and the lighter object moves upward with the same magnitude acceleration. Which of the following statements is true for the system consisting of the two objects? A) The center of mass remains at rest. B) The net external force is zero. C) The velocity of the center of mass is a constant. D) The acceleration of the center of mass is g, downward. E) None of the above statements are true.

51 University Physics (Prof. David Flory) Chapt_08 Saturday, October 06, 2007 Page 3 7. The center of mass of a system of particles has a constant velocity if: A) the forces exerted by the particles on each other sum to zero B) the external forces acting on particles of the system sum to zero C) the velocity of the center of mass is initially zero D) the particles are distributed symmetrically around the center of mass E) the center of mass is at the geometric center of the system 8. At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s. They move along nearby lines and pass without colliding. At the end of 2.0 s the velocity of the center of mass of the two-ball system is: A) 11 m/s, down B) 11 m/s, up C) 15 m/s, down D) 15 m/s, up E) 20 m/s, down 9. Two 4.0-kg blocks are tied together with a compressed spring between them. They are thrown from the ground with an initial velocity of 35 m/s, 45º above the horizontal. At the highest point of the trajectory they become untied and spring apart. About how far below the highest point is the center of mass of the two-block system 2.0 s later, before either fragment has hit the ground? A) 12 m B) 20 m C) 31 m D) Can't tell because the velocities of the fragments are not given. E) Can't tell because the coordinates of the highest point are not given. 10. Block A, with a mass of 4 kg, is moving with a speed of 2.0 m/s while block B, with a mass of 8 kg, is moving in the opposite direction with a speed of 3 m/s. The center of mass of the two block-system is moving with a velocity of: A) 1.3 m/s in the same direction as A B) 1.3 m/s in the same direction as B C) 2.7 m/s in the same direction as A D) 1.0 m/s in the same direction as B E) 5.0 m/s in the same direction as A

52 University Physics (Prof. David Flory) Chapt_08 Saturday, October 06, 2007 Page The center of mass of a uniform disk of radius R is located: A) on the rim B) a distance R/2 from the center C) a distance R/3 from the center D) a distance 2R/3 from the center E) at the center 12. The center of mass of a system of particles remains at the same place if: A) it is initially at rest and the external forces sum to zero B) it is initially at rest and the internal forces sum to zero C) the sum of the external forces is less than the maximum force of static friction D) no friction acts internally E) none of the above 13. Which one of the following statements is true? A) the center of mass of an object must lie within the object B) all the mass of an object is actually concentrated at its center of mass C) the center of mass of an object cannot move if there is zero net force on the object D) the center of mass of a cylinder must lie on its axis E) none of the above 14. The center of mass of Earth's atmosphere is: A) a little less than halfway between Earth's surface and the outer boundary of the atmosphere B) near the surface of Earth C) near the outer boundary of the atmosphere D) near the center of Earth E) none of the above

53 University Physics (Prof. David Flory) Chapt_08 Saturday, October 06, 2007 Page A system consists of two particles with masses of 2 kg and 4 kg, moving in opposite directions on the x axis. The velocity of the center of mass is (3m/ s) ˆi. The net momentum of the system: A) is zero B) is (6kg m/ s)i ˆ C) is (9 kg m/ s) ˆi D) is (12 kg m/ s) ˆi E) cannot be computed unless the velocities of the particles are given 16. Particle A has a mass of 1 kg and a speed of 3 m/s. Particle B has a mass of 2 kg. The speed of the center of mass of the two-particle system is 5 m/s. The greatest and least speed that particle B might have are: A) 6 m/s and m/s B) 3 m/s and 6 m/s C) 0 and 3 m/s D) 0 m/s and 9 m/s E) 5 m/s and 6 m/s 17. The x and y coordinates of the center of mass of the three-particle system shown below are: A) 0,0 B) 1.3 m, 1.7 m C) 1.4 m, 1.9 m D) 1.9 m, 2.5 m E) 1.4 m, 2.5 m

54 University Physics (Prof. David Flory) Chapt_08 Saturday, October 06, 2007 Page The velocity of the center of mass of a two-particle system is (2m/ s)i ˆ and the net momentum of the system is (8kg m/ s) ˆi. If the mass of one of the particles 3 kg the mass of the other is: A) zero B) 1 kg C) 2 kg D) 3 kg E) 4 kg 19. The center of mass of the system consisting of Earth, the Sun, and the planet Mars is: A) closer to Earth than to either of the other bodies B) closer to the Sun than to either of the other bodies C) closer to Mars than to either of the other bodies D) at the geometric center of the triangle formed by the three bodies E) at the center of the line joining Earth and Mars 20. Cart A, with a mass of 0.20 kg, travels on a horizontal air track at 3.0 m/s and hits cart B, which has a mass of 0.40 kg and is initially traveling away from A at 2.0 m/s. After the collision the center of mass of the two cart system has a speed of: A) zero B) 0.33 m/s C) 2.3 m/s D) 2.5 m/s E) 5.0 m/s

55 University Physics (Prof. David Flory) Chapt_08 Saturday, October 06, 2007 Page 7 Answer Key 1. E 2. D 3. A 4. B 5. D 6. E 7. B 8. C 9. B 10. B 11. E 12. A 13. E 14. D 15. D 16. A 17. C 18. B 19. B 20. B

56 University Physics (Prof. David Flory) Chapt_09 Wednesday, October 24, 2007 Page 1 Name: Date: 1. Vectors a and b each have magnitude L. When drawn with their tails at the same point, the angle between them is 30º. The value of a b is: A) zero B) L 2 2 C) 3L / 2 D) 2L 2 E) none of these 2. A watt second is a unit of: A) force B) power C) displacement D) speed E) energy 3. A 0.50-kg object moves on a horizontal frictionless circular track with a radius of 2.5 m. An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around. If it starts from rest, then at the end of one revolution the radial component of the force of the track on it is: A) 19 N B) 38 N C) 47 N D) 75 N E) 96 N 4. A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m. An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around. The work done by the external force as the mass makes one revolution is: A) 24 J B) 47 J C) 59 J D) 94 J E) 120 J

57 University Physics (Prof. David Flory) Chapt_09 Wednesday, October 24, 2007 Page 2 5. Three identical ideal springs (X,Y,Z) are arranged as shown. When a 4.0-kg block is hung on X, the block remains at rest when it is released with the spring elongated by 3.0 cm. When a 6.0-kg block is hung on Y, the block remains at rest when it is released with the spring elongated by: A) 2.0 cm B) 4.0 cm C) 4.5 cm D) 6.0 cm E) 9.0 cm 6. In raising an object to a given height by means of an inclined plane, as compared with raising the object vertically, there is a reduction in: A) work required B) distance pushed C) friction D) force required E) value of the acceleration due to gravity 7. A watt is: A) a kg m/s 3 B) a kg m 2 /s C) a kg m 2 /s 3 D) a kg m/s E) a kg m 2 /s 2

58 University Physics (Prof. David Flory) Chapt_09 Wednesday, October 24, 2007 Page 3 8. A man moves the 10-g object shown in a vertical plane from position P to position Q along a circular track of radius 20 m. The process takes 0.75 min. The work done by the man is about: A) 1 J B) 2 J C) 4 J D) 6 J E) 12 J 9. A crate moves 10 m to the right on a horizontal surface as a woman pulls on it with a 10-N force. Rank the situations shown below according to the work done by her force, least to greatest. A) 1, 2, 3 B) 2, 1, 3 C) 2, 3, 1 D) 1, 3, 2 E) 3, 2, 1

59 University Physics (Prof. David Flory) Chapt_09 Wednesday, October 24, 2007 Page A sledge (including load) weighs 5000 N. It is pulled on level snow by a dog team exerting a horizontal force on it. The coefficient of kinetic friction between sledge and snow is How much work is done by the dog team pulling the sledge 1000 m at constant speed? A) J B) J C) J D) J E) J 11. Two bodies, A and B, have equal kinetic energies. The mass of A is nine times that of B. The ratio of the translational momentum of A to that of B is: A) 1:9 B) 1:3 C) 1:1 D) 3:1 E) 9:1 12. A boy holds a 40-N weight at arm's length for 10 s. His arm is 1.5 m above the ground. The work done by the force of the boy on the weight while he is holding it is: A) 0 B) 6.1 J C) 40 J D) 60 J E) 90 J 13. A particle moves 5 m in the positive x direction while being acted upon by a constant force F = (4 N)i ˆ+ (2 N)j ˆ (4 N)kˆ. The work done on the particle by this force is: A) 20 J B) 10 J C) 20 J D) 30 J E) impossible to calculate without knowing other forces

60 University Physics (Prof. David Flory) Chapt_09 Wednesday, October 24, 2007 Page The weight of an object on the moon is one-sixth of its weight on Earth. The ratio of the kinetic energy of a body on Earth moving with speed V to that of the same body moving with the same speed on the Moon is: A) 6:1 B) 36:1 C) 1:1 D) 1:6 E) 1: An ideal spring is hung vertically from the ceiling. When a 2.0-kg block hangs at rest from it the spring is extended 6.0 cm from its relaxed length. A upward external force is then applied to the block to move it upward a distance of 16 cm. While the block is moving upward the work done by the spring is: A) 1.0 J B) 0.52 J C) 0.26 J D) 0.52 J E) 1.0 J 16. A Boston Red Sox baseball player catches a ball of mass m that is moving toward him with speed v. While bringing the ball to rest, his hand moves back a distance d. Assuming constant deceleration, the horizontal force exerted on the ball by his hand is: A) mv/d B) mvd C) mv 2 /d D) 2mv/d E) mv 2 /(2d) 17. An ideal spring is hung vertically from the ceiling. When a 2.0-kg mass hangs at rest from it the spring is extended 6.0 cm from its relaxed length. A downward external force is now applied to the mass to extend the spring an additional 10 cm. While the spring is being extended by the force, the work done by the spring is: A) 3.6 J B) 3.3 J C) J D) 3.3 J E) 3.6 J

61 University Physics (Prof. David Flory) Chapt_09 Wednesday, October 24, 2007 Page The work done by gravity during the descent of a projectile: A) is positive B) is negative C) is zero D) depends for its sign on the direction of the y axis E) depends for its sign on the direction of both the x and y axes 19. A 1-kg block is lifted vertically 1 m by a boy. The work done by the boy is about: A) 1 ft lb B) 1 J C) 10 J D) 0.1 J E) zero 20. The amount of work required to stop a moving object is equal to: A) the initial speed of the object B) the initial kinetic energy of the object C) the mass of the object times its acceleration D) the mass of the object times its initial speed E) the square of the initial speed of the object

62 University Physics (Prof. David Flory) Chapt_09 Wednesday, October 24, 2007 Page 7 Answer Key 1. D 2. E 3. B 4. B 5. E 6. D 7. C 8. C 9. E 10. B 11. D 12. A 13. A 14. C 15. A 16. E 17. A 18. A 19. C 20. B